Ultrafast ECHO is a new non invasive method for assessing stiffness of living tissues. It takes advantage of very fast imaging technologies (up to 20 000 images/sec) to measure the diffusion of pressure waves in the tissues. This pressure wave can be either natural (blood pressure), or generated by an very short ultrasonic impulsion at a given place. By using both modes, it is possible to have a precise cartography of tissue mechanical properties. This technique is applied to solid tissues such as breast or liver, but not yet currently to hollow tissues such as arteries. The aim of the present study is to compare the values of stiffness obtained with Ultrafast ECHO with the reference non invasive technique, the Echotracking, which measures stiffness by assessing the deformation of arteries in response to changes in blood pressure. On the physiological part, we will revisit old concepts of increased stiffness of hypertensive's arteries. Indeed, hypertension is associated with increased stiffness due to recruitement of collagen fibers, but also to chronic remodelling. We have shown before that this remodelling conducts to accumulation of arterial tissue of lesser intrinsic stiffness. The latter finding was done through models based on echotracking measurements. It will be interesting to see whether it holds true when stiffness is directly measured.